Of course, probably the largest change in the way the Internet works due to AdSense comes from the publishers’ point of view. Whereas one would previously have to jump through many hoops to get a website to even support itself now people are making fortunes off their sites. This leads to motivation for content, and resources for web surfers.
That generally means site publishers have to worry more about what content lies on their site, and the overall way their pages look rather then be concerned with the economic specifics of maintaining a site’s profitability. Although time is invested in adsense, a large capital investment is not.
It’s no surprise that the blogging phenomenon exploded when AdSense came out a few years ago. Anyone could just write a page about a subject he was passionate about and making a living out of it through AdSense.
And thirdly, one can’t ignore the impact AdSense has had over the casual everyday web surfer. Whereas people used to not even notice banners altogether (which psychologically is a very interesting thing to observe) the situation is completely different for text ads.